Can the Built Environment be Pre-Manufactured From Mass Timber?
Globally, the production of mass timber systems is increasing
exponentially, driven largely by the need for more sustainable ways of
delivering the built environment. Dr Robert Hairstans, Associate
Professor at Edinburgh Napier University and Head of the Centre for
Offsite Construction + Innovative Structures explains further.
Coinciding
with this is also a worldwide shift to more construction activities
being carried out offsite in factory environments, given the need for
improved levels of construction productivity combined with technological
advances that are being made, both mechanically and digitally. Mass
timber slab and beam components can be brought together and combined
with other materials offsite to form modular or volumetric units capable
of being enhanced to a high level of factory finish which equate to
turnkey solutions.
The mass timber family of products consists of
various form of solid laminate timber systems. However, it is the
panelised or slab forms of mass timber, primarily CLT, that have
particularly ‘moved the needle’ for use and application of timber in
construction given their capability to form whole building envelopes,
often in combination with mass timber beam products (glue-laminated
timber and laminated veneer lumber) and other construction materials in
hybrid forms.
The exponential growth in use of CLT is driven not
only by the environmental credentials of timber as a product, but also
by the structural attributes of the panels ascertained from this process
that allow timber to be used in building applications beyond normal
limitations. Once fabricated, the mass timber product is normally cut to
the required shape and size for the end application via CNC (computer
numeric control) saws which have the capability of cutting in almost any
direction with the precision necessary to form openings, services voids
or acoustic performance-enhancing profiles.
To streamline these
processes, the CNC operations will be linked to computer aided design
(CAD) and computer aided manufacture (CAM) software. It is worth noting
that this approach can also be utilised on NLT fabricated with aluminium
nails. These offsite manufactured mass timber products can then either
be shipped direct to site or formed into offsite volumetric modules that
can be taken to a high level of finish with windows, doors, external
cladding and internal linings and services included. Carbon Dynamic a
company based in the Scottish Highlands, are currently deploying this
approach in the delivery of student accommodation for the Dyson
Institute for Technology.
The utilisation of mass timber products
requires a change in design thinking particularly when the products are
to be further formed to create full volumetric units with an enhanced
level of finish. Designers need to take cognisance of the capabilities
of the mass timber manufacturing process (dimensional compatibility, CNC
cutting and routing capability) and follow-on production activities
(factory lifting, allowable space, available tools and equipment) to
create the volumetric system. In addition, the logistical arrangements,
from both a transport and site access perspective, need to be taken in
to account.
Information and communication technology (ICT) system
integration; understanding the full parameters of design for
manufacture and assembly (DfMA) as well as disassembly (DfMA+D) and
ensuring an early design freeze are therefore of high importance in
adding more value in the factory and ensuring successful project
delivery. DfMA+D takes cognisance of end of life or change of use, such
that the building components are demountable in the future for
reconfiguration or alternative applications.
Going forward,
digitisation and the emergence of integrated BIM platforms that
facilitate the interoperability of software utilised during each stage
of the mass timber production process can enhance the level of
information that resides within the built asset with a digital thread.
In theory, this can provide the capability of tracing the source
material back to the forest and thereby inform the product’s overall
environmental credentials. The use of virtual reality and augmented
reality (VR/AR) will facilitate knowledge exchange for upskilling and
early integration across the project team, as well as client and
customer understanding for improved decision-making. In-situ, the
performance of the unit and its interactions with its users can be
monitored, creating a feedback loop for future product optimisation or
maintenance.
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